Ethylbenzene is produced on commercial scale by the alkylation of benzene with ethylene. Due to periodic shortages and the hazardous nature of benzene, attempts have been made to produce ethylbenzene by methods other than alkylation of benzene with ethylene.
U.S. Pat. No. 2,745,887 discloses a process for treating with alkali metals cyclic hydrocarbons having 6 carbon atoms in the ring and containing at least two double bonds, at least one of them in the ring. However, this process is not feasible for commercial purposes since induction periods of 12-15 hours occur before the reaction is initiated, unless activators are added such as, for example, o-chlorotoluene, which reduce the induction period to 4-5 hours, or unless the process is carried out in the presence of extremely expensive and dangerous sodium hydride. However, even in these cases, only degrees of conversion of up to 71 percent are attained. Furthermore, it was found that this process does not yield useful results when vinylcyclohexene is used.
Furthermore, it is known from U.S. Pat. No. 3,903,185 that cycloolefins having 8 carbon atoms can be converted over catalysts of Subgroups VI to VIII, including the platinum group, of the Periodic Table of the elements, at temperatures of 350.degree.-450.degree. C., under pressures of 2.5-30 atmospheres absolute and in the presence of 0.2-20 m.sup.3 of hydrogen per kilogram of C.sub.8 -cycloolefin, to obtain ethylbenzene in rather satisfactory yields. However, this process is commercially very expensive, because it must be carried out at high temperatures, under pressure, and in the presence of hydrogen.
U.S. Pat. No. 4,048,243 discloses the dehydrogenation of cycloolefins by passing the cycloolefins over catalysts containing an alkali metal on a aluminum oxide support. The process is conducted at temperatures of about 20.degree.-150.degree. C. and pressure of about 0.8-2 atmospheres. This process requires the manufacture of a heterogeneous supported catalyst in a separate step which requires operation of the catalyst from the product in a later step.
Despite the disclosures of the prior art a need exists for the production of ethylbenzene in a method which produces ethylbenzene in high yields and in a cost-effective manner.